This invention relates to a sterilizable package or pouch made of a plastic member heat sealed to a paper member wherein the paper member is provided with a portion which can be separated from the package which carries indicia that changes color upon sterilization.
Such packages are made by marginally heat sealing a clear plastic laminate to surgical grade kraft paper or the like and have come into widespread use. The paper portion of such packages is designed to be sufficiently porous to permit gas or steam sterilization but is otherwise impervious to bacteria. The plastic laminate is heat sealable to the paper, stable under sterilization conditions, impervious to bacteria and permits visual identification of the package contents.
Such packages are used for medical implements that must be sterile prior to use. The manufacturer or user, such as a hospital or clinic, of such medical implements is supplied with a package heat sealed around three sides by the package manufacturer. The medical implement is then placed in the package and the fourth side is heat sealed to complete the marginal heat seal between the paper and the plastic. The package contents are then sterilized, either by exposure to ethylene oxide gas or by steam autoclaving and the package and its sterile contents can be stored for indefinite periods of time in a sterile condition.
To determine if a sealed package has been subjected to sterilization, it has been common practice to employ indicator inks that change color upon gas or steam sterilization and these indicator inks are typically printed on the exterior and/or interior of the paper member of the sterilizable package (cf. U.S. Pat. Nos. 3,093,242 to Huyck et al and 3,991,881 to Augurt). There are drawbacks to printing such indicator inks on the paper member in the area forming the heat sealed enclosure for the package contents with the plastic member. The main difficulty with indicator inks printed on either side of the paper member is that the package may be subjected to sterilization conditions which are sufficient to cause a color change in the indicator ink but insufficient to actually sterilize the package contents. With an indicator ink printed on the outside of the paper member the color change will occur as soon as the indicator ink comes in contact with steam or ethylene oxide gas and long before either gas penetrates the paper member and sterilizes the package contents. Printing the indicator ink on the inside of the paper member is an improvement but again, the ethylene oxide gas or steam in passing through the paper member comes in contact with the indicator ink before reaching the package contents. To cope with these problems, manufacturers and hospitals have to follow sterilization procedures with a built-in margin of safety to ensure that the package contents are sterilized which means using high sterilization temperatures over a sustained period of time. Because of these drawbacks, the indicator inks printed on the inside or the outside of the paper member simply say that the package has been put through sterilization but it is left up to the technician to ensure that the correct sterilization procedure has been observed to effectively sterilize the package contents.